The present invention relates to a private branch exchange with the Personal Handyphone System (PHS) function, and more particularly to multiple private branch exchanges which can use the same system call sign.
A conventional private branch exchange (PBX) with the PHS function reads the system call sign (SYS-ID) from a control cell station (control CS), stores the system call sign in the PBX, and writes data to general CSs belonging to the PBX. This prevents a plurality of PBXs from setting the same SYS-ID for (or in) general cell stations (general CSs).
An earlier patent disclosure dealing with this is found in Japanese Patent Publication Kokai JP-A No. Hei 4-70021. In this patent publication, a codeless telephone system is disclosed in which a mobile station has the same ID number as that of the PBX. This system allows mobile stations of multiple PBXs, connected via a leased line and having the same ID number, to send and receive calls to establish communication.
However, in the course of the investigations toward the present invention the following problems have been encountered. Namely as described above, two or more conventional private branch exchanges (PBXs), each with the PHS function, cannot assign the same SYS-ID to multiple general CSs. This means that a mobile station (PS) which moves from one PBX to another cannot connect to general CSs.
The present invention seeks to solve the problems described above. It is an object of the present invention to provide a private branch exchange which may assign the same SYS-ID to general CSs for use in a plurality of private branch exchanges.
Further objects of the present invention will become apparent in the entire disclosure.
To achieve the above object, in one aspect of branch of the present invention there is provided a private branch exchange comprising a control cell station and communicating with at least one mobile station,
wherein, the private branch exchange comprises
(a) means for reading a system call sign based on group information on a group associated with an allocated location of the control cell station, said system call sign corresponding to the group from any of private branch exchanges storing the system call sign corresponding to said group, and
(b) means for storing said system call sign also in a cell station in any of a plurality of private branch exchanges which are connected with said private branch exchange, provided that the cell station belongs to the same group of said control cell station.
According to a second aspect of the present invention, there is provided a private branch exchange network system comprising a network of plurality of private branch exchanges, each comprising a control cell station and communicating with at least one mobile station,
(a) in which databases of the private branch exchanges may be cross-referenced, and
(b) in which a control cell station allocated to each private branch exchange may be uniquely identified in each group with a call area number and a cell station number,
(c) each of said private branch exchange comprising:
(c1) a node unit database in which PBX identification information on said private branch exchange and group information associated with an allocated location of the control cell station are stored;
(c2) a network common database in which the PBX identification information identifying the private branch exchange to which said control cell station is allocated is stored, said PBX identification being associated with information on the group to which said control cell station belongs and with a call area number and a cell station (CS) number of each cell station; and
(c3) means for copying the network common database to any of other private branch exchanges at a regular interval,
(d) wherein a first private branch exchange to which said control cell station is allocated:
(i) stores a system call sign of the group to which the control cell station belongs into the node database of the first private branch exchange,
(ii) when a general cell station allocated to a second private branch exchange is started, said system call sign is read either from the data base of a second private branch exchange to which the general cell station is allocated or from the database of a private branch exchange to which the control cell station corresponding to the group of said general cell station belongs, and
(iii) said system call sign is stored also in any general cell station belonging to the same group of said control cell station in a plurality of the private branch exchanges connected each other.
Further aspects and features of the present invention will become apparent in the entire disclosure including the appended claims. The features of the dependent claims are incorporated herein by reference thereto.